1. Field of the Invention
This invention generally relates to vehicles and more particularly to a platform vehicle that can negotiate obstacles such as stairs.
2. Description of Related Art
Today, there are increasingly complex demands for robotic systems outside a modern factory floor. One significant problem, at present, is that wheeled platforms have difficulty navigating over uneven terrain, and traversing obstacles. While significant work has been done on bipedal and multi-legged robots, these systems typically have much higher power requirements than wheeled platforms. Wheeled platforms are, perhaps, the most efficient mechanisms for moving across any surface. Legged platforms require power both to move the platform horizontally across the surface, and require additional power to both support the platform and to lift and move the legs themselves. The wheel provides a passive support to the load, negating the need for the power needed to lift the platform. However, wheels are only efficient if the surface over which they travel is flat and relatively smooth, and wheels fail if there are either vertical obstacles, or significant voids in the surface. Hence, wheels have shown their worth in carefully engineered environments, and have failed in more complex domains.
Such uneven terrain may include vertical discontinuities, steps, and stairs, and situations where those surfaces are potentially covered with a variety of debris. For instance, if a traditional wheel were approaching a curb from the road surface, the curb would present a vertical obstacle, over which the wheel would have to climb. Since the only driving force on the wheel is the forward rotational motion, the geometry of the wheel and the curb has to translate the forward motion into upward motion, and thus raise the center of mass of the wheel. If the radius of the wheel is sufficiently large with respect to the curb, this transfer of energy is relatively smooth and effective. However, as the radius of the wheel approaches the height of the curb, the energy transfer becomes less effective, until the wheel fails to climb obstacles that exceed its radius.
Currently there is no mechanism that provides generally passive support for the platform to which it is attached, provides power for movement over surfaces, and can provide movement across a wide variety of surfaces, including those found in rough terrain, urban environments, indoors, and disrupted and partially engineered settings.